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8631581 
Meetings & Symposia 
CFC-free polyurethane pipe insulation foams for use in district heating systems 
Broennum, T 
1991 
Publ by Technomic Publ Co Inc 
Nice, Fr 
Polyurethanes World Congress 1991 
243-249 
English 
Polyurethane insulated pipes used in district heating systems have been widely accepted and the market has grown considerably over the past decade. However, the worldwide concern about the depletion of the stratospheric ozone layer has led to major R&D effort to develop CFC-free systems, as chlorofluorocarbons have been identified as important contributors to this problem. We have investigated the effect of the total replacement of CFC-11 on the processing and physical properties of the composite. The blowing agents considered were carbon dioxide, via the water/isocyanate reaction, and dual blown systems based on carbon dioxide and HCFCs such as 142b. The use of these blowing agents has required the development of new polyols to overcome problems encountered in processing and end properties when increased water levels are used in the formulations. Techniques such as thermal mechanical analysis and foam aging experiments have been applied in our laboratory to evaluate foams produced from development polyols. The result of industrial trials showed that using optimised polyols in combination with these blowing agents, the overall properties and heat resistance of the pipe composite could be maintained or improved. The only disadvantage when a fully water blown system was used, an increase in the foam thermal conductivity, could be minimised by application of the dual blown system.